Incandescent bulbs (and fluorescent bulbs) are typically formed with a frangible enclosure (e.g. glass) that maintains a vacuum or environment to prevent oxidation of the glow filament (e.g. tungsten) or maintain function during operation. The incandescent bulb can be coated by dipping it into a silicone dispersion consisting of excess solvent (e.g., xylene) and curable silicone rubber with the subsequent removal of the solvent. Other methods include initially coating the incandescent bulb with an organic solvent-based silicone composition followed by solvent removal and/or treating the coated lamp bulb surface with a solvent-based silicone overcoat. Commercial incandescent light bulbs with a protective coating can be made using a paste-like silicone rubber compound that requires large amount of solvent to dilute the silicone rubber compound down to a high solvent containing solution to allow light bulb coating. Unfortunately, hazardous and flammable solvents such as toluene, xylene are the required solvents.
While various silicone transparent dielectric compositions are otherwise known for treating the bulbs of incandescent lights to enhance their shatter resistance, issues specific only to LED lamps remain regarding reducing or completely preventing access to the components within a frangible enclosure, the use of phosphors, the use of internal atmospheres or environments within the enclosure, as well as significant environmental concerns with solvent-based coatings. Presently, for certain types of LED lamps, protection against fire and shock hazard is required by safety agencies (e.g., Underwriters Laboratories). Protection against fire and shock is typically provided by a glass globe which covers the exposed LEDs, LED PCB, and electric connector. Because the glass is the enclosure for the product, stringent requirements are placed on the adhesive used to hold the globe onto the heat sink. Protection against the shock hazard in case the glass breaks can be augmented by a silicone coating over the glass or the use of a plastic enclosure, both of which are less than desirable. The silicone coating keeps the glass intact when it breaks and restricts access to the LED board inside. The coating process is costly, time consuming and generates waste, typically involving dipping of the glass globe in silicone, allowing for drip time and cure time in an oven at a high temperature. The process affects cosmetic appearance and gives the glass globe an elastomeric or rubbery texture and aesthetics.